SMACH专题（三）----几种State类型

　　状态机提供了若干种状态，包括了Generic State，CBState，SimpleActionState (ROS)，ServiceState (ROS)，MonitorState (ROS)。下面分别介绍它们的用法和例子。

一、CBState回调状态

　　将一个函数封装成状态，这种状态成为回调状态。这种函数非类中的函数，而是一般的函数。下面是一个例子：

 #!/usr/bin/env python
 # license removed for brevity

 import rospy
 from std_msgs.msg import String
 import math
 import random
 from smach import CBState, StateMachine
 from smach_ros import IntrospectionServer
 import smach

 @smach.cb_interface(
                 output_keys=['xyz'],
                 outcomes=['outcome1','outcome2'])
 def fun_cb(ud,x0, x, y, z):
     '''
     callback function, which is called in CBState way, it seems to be used by
     function, but the class'funtion
     '''
     #x0 is the value of  cb_args=[10], equal to 10
     dist = math.sqrt(x0*x0+x*x+y*y+z*z+100*random.random())
     ud.xyz = dist
     if dist > 10:
         return 'outcome1'
     else:
         return 'outcome2'

 class Test_CbState():
     def __init__(self):
         rospy.init_node('smach_example_callback_state')
         self.sample_name = "cbstate"  

     def test(self):
         '''
         test Callback State Machine
         '''
         self.sm = StateMachine(outcomes = ['outcome3'])
         with self.sm:
             StateMachine.add('Test_CB',CBState(fun_cb,
                                                cb_args=[10],
                                                cb_kwargs={'x':1,'y':2,'z':3}),
                                                {'outcome1':'outcome3','outcome2':'Test_CB'})
         sis = IntrospectionServer('test_cb_state', self.sm, '/SM_ROOT')
         sis.start()

         self.sm.execute('Test_CB')

         rospy.spin()
         sis.stop()

 if __name__ == '__main__':
     '''
     main funtion
     '''
     test_sm_cbstate = Test_CbState()
     test_sm_cbstate.test()
             

　　状态图，如下图所示：

　　参考资料：

　　　　[1]. CBState